Mobile communication devices have become increasingly common in current society for providing wireless communication services. The prevalence of these mobile communication devices is driven in part by the many functions that are now enabled on such devices. Increased processing capabilities in such devices means that mobile communication devices have evolved from being pure communication tools into sophisticated mobile multimedia centers that enable enhanced user experiences.
The redefined user experience requires a higher data rate offered by wireless communication technologies, such as fifth generation new radio (5G-NR) and Wi-Fi that typically operates in higher frequency spectrums. To achieve higher data rates with increased robustness in the higher frequency spectrums, sophisticated power amplifiers (PAs) may be employed to increase output power of radio frequency (RF) signals (e.g., maintaining sufficient energy per bit) prior to transmitting the RF signals.
Envelope tracking (ET) is a power management technology designed to improve efficiency levels of the PAs to help reduce power dissipation in the mobile communication devices. As the name suggests, an ET circuit is configured to generate a modulated voltage that keeps track of a target voltage envelope and provide the modulated voltage to the PAs for amplifying the RF signal(s). However, the ET circuit has inherent output impedance that can interact with an inherent load of the PAs, particularly at a higher modulation bandwidth (e.g., >100 MHz). Consequently, the modulated voltage may be degraded, thus leading to distortions being created outside the modulation bandwidth. As such, it may be desirable to control the output impedance of the ET circuit to help reduce the distortions associated with the higher modulation bandwidth.